Mechanical coin checking devices are generally known and their construction consists of a basic body in which a coin running channel is disposed and which abuts against a coin slot. A plurality of checking sensors is disposed on the coin running channel, i.e. in the walls thereof, which check for example the dimensions of the coin and the metallic properties. If a coin has been detected as genuine, it is conducted from the coin channel into an acceptance channel which is connected to a cash box and at which a confirmation photoelectric barrier is disposed, which detects the passage of a coin to be conducted into the cash box and emits a so-called credit signal to an automatic machine control, i.e. to a control which controls the course of the processes in an automatic machine, such as a vending machine or for example an automatic washing machine in which the coin checking device is disposed. If a coin has been detected as not being genuine by the checking devices, is conducted into a return channel.
In order to avoid manipulation and interventions by foreign objects, blocking elements are disposed in the region of the coin channel and prevent the introduction of foreign objects, such as wire elements, cardboard strips or the like, which are intended to affect the confirmation photoelectric barrier. However, it has been shown that the blocking elements present do not suffice for all fraudulent possibilities, it has been shown for example that manipulation is possible, despite the blocking elements, with soft flexible objects.